Yugoslavia came under a barrage of Nato air and missile strikes last night after a defiant Slobodan Milosevic ignored repeated warnings from alliance leaders to back down over Kosovo.

Huge explosions rocked the Kosovan capital, Pristina, just after 7pm GMT, and air raid sirens and blasts were heard in Belgrade immediately after confirmation from Brussels that Nato had launched its first attack on a sovereign state in the hope of averting a humanitarian catastrophe and wider Balkan war.

Within the first hour, strategic and industrial targets from Novi Sad in northern Serbia, through its sister republic Montenegro, to Kosovo in the south were reported hit. Serbian forces in Kosovo are on the offensive against ethnic Albanian rebels.

Yugoslav military sources last night claimed seven towns had been hit in the first wave of attacks, and that women and children were among those killed.

The operation was last night given the name Allied Force, and the US contribution dubbed Noble Anvil.

Some 80 Western warplanes, including stealth bombers, F-16s and F-18s, took off from the Nato airbase at Aviano, north-east Italy. Witnesses said 11 A117 stealth bombers, A10 ground attack planes, EA6B prowlers, C130s, CF18s, F16s, F15s and F18s from the US, Britain, Spain, Portugal and Canada were airborne.

The British involvement included Harrier GR7 aircraft and cruise missiles launched from the nuclear submarine HMS Splendid. Tomahawk missiles were fired from American ships in the southern Adriatic.

Tony Blair, speaking at the European Union's Berlin summit, said: 'We are taking this action to prevent Milosevic from continuing to perpetuate his vile oppression against innocent Kosovar civilians.

'Britain is a peaceful nation. We are a peaceful nation that takes no joy in war but we know from our own history and our own character that there are times when you have to stand up and fight for peace. We have a duty to see justice is done.'

Before the unprecedented attacks began, US president Bill Clinton talked of a struggle 'between good and evil' and later told a White House news conference: 'Only firmness now can prevent greater catastrophe later.'

'Clear responsibility for the air strikes lies with President Milosevic who has refused to stop his violent action in Kosovo and has refused to negotiate in good faith,' declared the Nato secretary-general, Javier Solana. 'The time has now come for action.'

The Russian reaction was furious. President Boris Yeltsin, who made a last-ditch appeal to President Clinton not to take 'the tragic step' of bombing, said he was 'deeply shocked'. He called for an immediate session of the United Nations Security Council and ordered a halt to military co-operation with Nato.

The Russian ambassador to the UN, Sergei Lavrov, said: 'If force is used, we believe the Security Council cannot remain silent.' And Russia said it reserved the right to take military measures, although it was unclear what these might be.

Bari and Brindisi airports in Italy were closed, as were those in Bosnia, as Europe's biggest single military action since 1945 was launched.

EU leaders had hoped until the last minute that Mr Milosevic might back down.

'One phone call from Milosevic would be enough,' said Germany's foreign minister, Joschka Fisher. 'That is possible at any time and the whole military process will be stopped.'

Neutral Austria marred the sense of solidarity by saying it would close its airspace to Nato aircraft attacking Yugoslavia because there was no UN mandate for the campaign. Ireland and Finland also insisted they did not back air strikes.

In Belgrade, Mr Milosevic insisted he had been right to reject international demands that he accept autonomy for Kosovo and a Nato-led force to police the deal. 'We shall defend the country if it is attacked,' he added in a brief television address.

The attacks were authorised by General Wesley Clark, Nato's top commander. He, in turn, was given the formal go-ahead on Tuesday evening, just hours after last-ditch talks in Belgrade between President Milosevic and US special envoy Richard Holbrooke ended in failure.

Before the attacks began, Gen Clark gave an impassioned statement about why they were needed.

'We have to stop leaders who are not prepared to look to the future, who continue to look to the past, who are not prepared to look to the 21st century and continue to do terrible things to their people,' he said.

Belgrade took the first attacks in its stride. No extra security was posted around Mr Milosevic's residence in the Dedinje district. People were walking home.

The atmosphere remained relaxed until just after 7pm when there were two bright orange flashes to the north of the city so far away that there was no sound. They came 10 minutes before the sirens sounded. Even then traffic continued to flow along the streets and the lights stayed on. But telephone lines were jammed as families rang friends and families in a desperate attempt to find out what was happening.

Nato's initial aim was to heavily damage Yugoslavia's air defence network in order to increase the effectiveness of the wider air offensive that is expected to follow. Hundreds of Nato warplanes are now expected to strike against Yugoslav military targets involved in attacks on ethnic Albanians in Kosovo.